Free volume in glassy poly(arylene ether ketone)s

Abstract

Amorphous polyarylene ether ketones were examined in the glassy state by positron annihilation lifetime spectroscopy (PALS) and in the melt by standard rheological techniques. Specimens were well‐characterized fractions of two isomeric structures. PALS clearly shows that the polymer with meta linkages in its backbone contains larger voids (> 0.25 nm radius). Thus despite their similar bulk densities, the two materials must pack very differently on a local scale. On the other hand, the free volumes inferred from the WLF treatment of melt viscosity data are practically identical in both materials ca. 4% at Tg. The comparison between techniques sheds some light on the distribution of free volume. © 1992 John Wiley & Sons, Inc.

Multiscale modeling of polymer materials using a statistics-based micromechanics approach

“…The functional forms of Equations (18) and (19) clearly assign higher probabilities to microstates with lower energies. Results Tables 1 and 2 show the results obtained from the MD simulations of each microstate of the polyimide and polycarbonate materials, respectively.…”

“…The probability distributions described by Equations (18) and (19) obey the normalization condition of Equation (17). The functional forms of Equations (18) and (19) clearly assign higher probabilities to microstates with lower energies.…”

“…Many combinations of the conformations of multiple polymer chains are possible for a particular RVE in an equilibrated or non-equilibrated state because of the finite entropy of the material for any temperature above 0 K owing to the dynamics of the constituent chains [2,[14][15][16]. As a result, the molecular structure, and thus density, of a polymer material varies substantially on the nanometer length-scale [16][17][18][19][20][21][22][23]. The large number of possible conformations for a specific volume of a polymer material constitutes a conformation space.…”

Influence of representative volume element size on predicted elastic properties of polymer materials

“…The finite-chain network can only sample a small portion of the conformational space of the bulk polymer. As a result, the physical properties of a polymer can vary substantially on the nanometer length-scale [14][15][16][17][18][19][20][21][22][23]. Similarly, the RVE size can influence the predicted mechanical properties of a polymer [24] using multiscale modeling techniques.…”

Synthesis, morphology, and melting behavior of poly(ether ether ketone) of different molecular weights

“…10 Over the last two decades, to accommodate the enormous applications, the crystallization and melting behavior have been studied extensively via differential scanning calorimetry (DSC), [11][12][13][14][15][16] smallangle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD), [17][18][19][20][21][22][23][24] thermomechanical analysis, [25][26][27] transmission electron microscopy (TEM), 28,29 and optical microscopy (OM). [20][21][22][23][24][25][26][27][28][29][30][31][32][33] The process of bulk crystallization of PEEK was studied through the separation of the nucleation and growth steps by Medellin-rodriguez and Phillips. 34 It was observed that a first slope at low crystallization times is associated with massive heterogeneous nucleation and/ or local-order-promoted primary nucleation of spherulitic crystal.…”